SERUM PERCENT-FREE PSA DOES NOT PREDICT EXTRAPROSTATIC SPREAD OF PROSTATE-CANCER

Percent-free prostate-specific antigen (proportion of free prostate-sp ecific antigen [PSA] to total PSA) has been shown recently in studies on frozen serum samples to be more useful than total PSA alone in dist inguishing prostate cancer from benign conditions of the prostate glan d. The primary purpose of our study was to determine whether percent-f ree PSA could predict extraprostatic spread of prostate cancer. We als o sought to evaluate the freeze-thaw stability of free PSA. Percent-fr ee PSA values in fresh serum samples were compared with those in aliqu ots subjected to one to five freeze-thaw cycles. Percent-free PSA valu es in frozen serum samples from 130 men undergoing radical prostatecto my for clinically localized prostate cancer were compared across patho logic stages. Free PSA levels remained stable for up to five freeze-th aws. Great overlap was found in percent-free PSA values for men with o rgan-confined disease and those with extraprostatic spread. These resu lts indicate that multiple freeze-thaw cycles do not significantly aff ect free PSA levels and percent-free PSA is not useful in identifying ideal candidates for radical prostatectomy.